#include <iostream>
#include <fstream>
#include <algorithm>
#include <cmath>
#include <climits>
#include <math.h>
#include <vector>

using namespace std;

const int oo = (int) (1e9);

ifstream in("fact.in");
ofstream out("fact.out");

int k, st, dr, mij;

int zeros(int x){
    int nr = 0;
    for(int i=5; i<=x; i*=5){
        nr+=x/i;
    }
    return nr;
}
 
int main() {
    in >> k;
    st = 1;
    dr = oo;
    while(st < dr){
        mij = st + (dr - st) / 2;
        if(zeros(mij) < k){
            st = mij + 1;
        }else{
            dr = mij;
        }
    }
    if(zeros(st)==k){
        out << st;
    }else{
        out << -1;
    }

    return 0;
}